pipes.rs: add missing count on fallback

Author: oech3

src/uucore/src/lib/features/pipes.rs

@@ -215,6 +215,7 @@ pub fn send_n_bytes(input: impl AsFd, target: impl AsFd, n: u64) -> std::io::Res
                         let mut drain = Vec::with_capacity(s);
                         broker_r.take(s as u64).read_to_end(&mut drain)?;
                         RawWriter(&target).write_all(&drain)?;
+                        bytes_written += s as u64;
                         break true;
                     }
                 }